Polymerization of unsaturated compounds in the presence of a peroxide and a hydrogenhalide



Patented July 13 1948 POLYMERIZATION OF UNSATURATED COM- POUNDS IN THEPRESENCE OF A PEROX- IDE AND A HYDROGEN HALIDE Edward C. Shokal,Oakland, Gall! assignor to Shell Development Company, San Francisco,Calif., a corporation Delaware No Drawing. Application March 21, 1944,Serial No. 527,490

This invention relates to the polymerization of unsaturated compounds inthe presence of oxygen-containing catalysts.

. Peroxides and other oxygen-yielding substances are common andeffective catalysts for the polymerization or unsaturated organiccompounds. In many cases, however, peroxides give rise tocolor-formation, i. e. discoloration, during polymerization,.theintensity of the produced color being directly related to the amount ofcatalyst present. Discoloration is generally objectionable.

An object of the present invention is to provide for reducingcolor-formation in the polymerization of unsaturated compounds in thepresence of oxygen-containing catalysts. Another object is to providenew polymerizable compositions. Another object is to provide an improvedmethod of polymerizing unsaturated resin-forming compounds. Anotherobject is to provide peroxidecatalyzed polymers of improved quality.Another object is to provide new synthetic resins. Other objects will beapparent from the description of the invention given hereinafter.-

These objects are accomplished in accordance with the present inventionby the polymerization of polymerizable unsaturated compounds whichdiscolor when subjected to polymerization with an oxygen-yieldingcatalyst, in the presence of a small amount of a-hydrogen halide. It hasnow been found that hydrogen halides are capable of reducing thediscoloration developed in the production of resins by polymerizationreactions catalyzed by peroxides and the like. When the amount of halidepresent is small relative to the amount of resin, the hardness and otherphysical properties of the resin are not significantly adverselyafiected.

6 Claims. ((31. zoo-1&4 I

Compounds which can be polymerized in the hydrogen atom of at least oneof the carboxyl groups is replaced by an unsaturated hydrocarbonradical.

A- preferred subgroup, which consists of those I compounds with whichthe importance of the invention is most apparent, comprises esters ofpolycarboxylic acids with unsaturated alcohols of aliphatic character.

Suitable unsaturated alcohols whose ester radicals may constitute a partof the compounds with which the invention is particularly'concerned arethose having an unsaturated linkage of aliphatic character between twocarbon atoms, one of which is directly attached to a carbon atom towhich is directly attached an alcoholic hydroxyl group. These compoundscan be described also as alcohols of aliphatic character having anunsaturated linkage between two carbon atoms, at least one of which isnot more than once removed from the alcoholic hydroxyl group.

One subgroup of unsaturated alcohols within the foregoing definitionconsists of allyl-type alcohols. Allyl-type alcohols are unsaturatedcompounds having an oleflnic double bond of aliphatic character-betweentwo carbon atoms, one of which is directly joined to asaturatedicarbinol carbon atom. They have a structure which may berepresented by the general structural formula Preferred allyl-typealcohols have a terminal methylene group attached by an oleflnic doublebond to a carbon atom which is directly attached to a saturated carbinolcarbon atom, as represented by the formula Allyl-type alcohols useful inthe present invention preferably have not more than about eighteencarbon atoms and have at least one unsaturated carbon-to-carbon' linkagefor each six carbon atoms.

Representative examples of preferred allyl-type alcohols are thefollowing: allyl alcohol, methallyl alcohol, ethallyl alcohol,chloroallyl alcohol, buten-l-ol-3, penten-1-ol-3, hexen-1-ol-3,B-me'thyl-buten-l-ol-S, 3-methyl-penten-l-ol-3, 2-methyl-buten-1-ol-3,2-methyl-penten-1-ol-3, 2,3-dimethyl-buten-l-ol-3, hepten-1-ol-3,-methylhexen-1-ol-3, 5-methyl-hexen-1-ol 3, 4,&'-dimethyl-penten-l-ol-S,octen-l-ol-3, fi-meth'ylhepten-l-ol-Ii, 4-methyl-hepten-l-ol-3, ,d'-di=methyl-hexen-l-ol-S, 3-phenyl-propen-=l-ol-3, 3- tolyl-propen-1-ol-3,.3-xylyl-propen-1-ol-3, 4- phenyl-buten-l-ol-li, 4-tolyl-buten-L- ol 3, 4xyly1-buten-1-ol-3, 3-naphthyl-propen l-ol-3, 4- chloro-buten-l-ol-il,pentadien-l,4-ol-3, hexen-=1- yn-5-ol-3, 2-methyl-penten-1-yn-4-ol-3,and 2,5- dimethyl-hexadien-l,5-ol-4. Other allyl-type alcohols' arecrotyl alcohol, tiglyl alcohol, 3-chlorobuten-2-ol-1, cinnamy1 alcohol,hexadien-2,4-ol-1, hexadien-2,5-ol-1, butadien-2,3-ol-1, hexadien-3,5-01-2, 2-methyl-hexen-2-o1-1, 2-methyl-penten-2-ol-1,3,7-dimethyl-octadien-2,l-ol-l, cyclopenten-2-ol-1, cyclohexen-2-ol-1,etc.

Another subgroup of suitable unsaturated alcohols consists ofalpha-unsaturated aliphatic alcohols, e. g. vinyl-type alcohols, whichare compounds having a double bond of aliphatic character between twocarbon atoms, one of which is directly attached to an alcoholic hydroxylgroup, as represented by the general formula f the vinyl-type alcohols apreferred subgroup consists of compounds having a terminal methylenegroup attached by an olefinic double bond to a carbinol carbon atom, asrepresented by the general formula Examples of preferred vinyl-typealcohols are vinyl alcohol, iso-propenol, buten-1-ol-2, etc. Examples ofother vinyl-type alcohols are propen-lol-1, buten-l-ol-l,cyclohexen-l-ol-l, cyclopenten-l-ol-l, etc. Vinyl alcohol is thepreferred specific alpha-unsaturated alcohol.

Other unsaturated alcohols whose radicals may constitute part of thecompounds with which the invention is concerned are those having atriple bond of aliphatic character between two carbon atoms. one ofwhich is directly attached to a saturated carbon atom, which in turn isdirectly attached to an alcoholic hydroxyl group as represented by thegeneral formula Another group consists of sulfonyl-containingpolycarboxylic acids, e. g. sulfonyl diglycolic, sulfonyl dihydracrylic,sulfonyl dilactic, etc., acids. Another and preferred group consists ofaromatic polycarboxylic acids, i. e. acids having two or more carboxylgroups directly attached to an arcmatic ring. Among the many suitablearomatic polycarboxylic acids are phthalic, isophthalic, terephthalic,naphthalene dicarboxylic, dimethyl phthalic, dichlorophthalic, etc.,acids and the corresponding higher polycarboxylic acids. Among the manyother suitable acids are tetrachlorophthalic acid and the otherpolyhalobenzene polycarboxylic acids.

Simple or mixed esters may be used.

Examples of suitable polymerizable unsaturated aromatic polycarboxylicacid esters are diallyl phthalate, dimethallyl phthalate, dichloroallylphthalate, diethallyl phthalate, diallyl isophthalate, dimethallylisophthalate, allyl chloroallyl phthalate, allyl crotyl phthalate,diallyl tetrachlorophthalate, dimethallyl tetrachlorophthalate, divinylphthalate, di-isopropenyl phthalate, allyl vinyl phthalate, methallylvinyl phthalate, chloroallyl vinyl phthalate, allyl isopropenylphthalate, methallyl isopropenyl phthalate, allyl(butene-1-yl-2)phthalate, crotyl vinyl phthalate, crotyl propargyl phthalate, allylpropargyl phthalate and the corresponding esters of the higherpolycarboxylic aromatic acids. The compound specifically preferred byreason of its stability under polymerization conditions, the ease andcomparative cheapness of its preparation, its ready polymerizability andthe high quality and reproducibility of products containing the polymeris diallyl phthalate.

Examples of suitable unsaturated esters of saturated aliphaticpolycarboxylic acids are diallyl oxalate, divinyl oxalate, diallylmalonate, diallyl adipate, allyl vinyl adipate, diallyl citrate, etc.Examples of suitable unsaturated esters of ethereal oxygen-containingpolycarboxylic acids are diallyl diglycolate, diallyl dihydracrylate,diallyl dilactate, dimethallyl diglycolate, allyl vinyl diglycolate,etc. Examples of suitable esters of sulfonyl-containing carboxylic acidsare diallyl sulfonyl diglycolate (also known as diallyl dimethylsulfonealpha,alpha-dicarboxylate diallyl sulfonyl dihydracrylate (also known asdiallyl diethylsulfone beta,beta'-dicarboxy1ate), etc.

In the case of esters of unsaturated alcohols with polycarboxylic acidsof the class defined herein but a single carboxyl group of the acid maybe esterified with an unsaturated alcohol, the remaining carboxyl groupor groups being unesterified or esterified with a saturated alcohol; orthe carboxyl groups of the acid may be esterified with two or moredifferent unsaturated alcohols.

Polymerization is effected in accordance with the invention in thepresence of an oxygen-yielding catalyst, particularly one which normallygives rise to color-formation during or after polymerization. The mostnotable example is benzoyl peroxide. Others are tertiary alkylhydroperoxides, such as tertiary butyl hydroperoxide (often calledsimply tertiary butyl peroxide), and di(tertiary alkyl) peroxides, suchas di(tertiary butyl) peroxide. Other organic peroxides result incolor-formation, as do many other oxygenyielding compounds, e. g.perborates, persulfates, etc. The catalysts can be used alone, or inadmixture with one another, or with other polymerization catalysts. Insome cases polymerization is desirably efiected in the presence of botha catalyst and an inhibitor of polymerization.

The optimum amount of catalyst employed in the polymerization isdependent upon many factors and no general limits can be given; Ingeneral, it is preferred to employ as little catalyst as is required tobring about the reaction in a commercially feasible period of time underpractical operating conditions. Amounts of catalysts as small as 0.01%by weight of the polymerizable material can be used. On the other hand,amounts as great as 10% or more may be employed. More usually the rangeis from about 1% to about 5% of benzoyl peroxide catalyst or f '5 itsequivalent by weight of polymerizable material. In general, the greaterthe quantity or catalyst present the greater is the discoloration undergiven conditions and the more advantageous is the use of thecompositions and technique of the invention.

' Any of the hydrogen halides may be present during polymerization inaccordance with the invention. Hydrogen bromide is particularlyefiective. Hydrogen iodide, hydrogen chloride and hydrogen fluoride maybe used.

It is not essential that the hydrogen halide be added as such to thepolymerization mixture. It may, for instance, be formed in situ by thereaction 01 one or more suitable reactive substances. The halidemodifier may be added to substantially unpolymerized monomer, or topartially polymerized material.

The amount of hydrogen halide employed should not be great since it hasbeen found that the hardness and other physical properties of thematerial may be deleteriously affected thereby.

In general it is preferred to use no more than one part of hydrogenhalide per 100 parts of polymerizable material, and in most cases 0.5part is sufiicient. 0.5 part of hydrogen halide per 100 parts of thepolymerizable material effects a very substantial reduction incolor-formation without significantly reducing the hardness of theresinous Y polymer. Smaller amounts, e. g. 0.1% or even less, are oftensuilicient. In those cases, however, where the achievement or maximumhardness is not as important as color reduction, amounts larger than 1%,e. g. 2% to 5%, or even somewhat more, may be used.

Polymerization reactions in accordance with the invention can be carriedout in a continuous or batchwise manner, at atmospheric,superatmospheric or reduced pressures. The invention is particularlyimportant in the production of cast shapes by the polymerization ofresin-forming polymerizable compounds in a mold in the substantialabsence of solvent or non-solvent diluent.

Polymerization is generally carried out under the influence of heat, thetemperature used being be separated from its mixture with polymer bysolvent extraction, distillation or other methods. The-polymer may-thenbe worked up in any known or special manner. In the case of manycompounds, particularly in the ease of compounds havingtwo or morenon-conjugated polymerizable unsaturated linkages in the molecule, theseparated polymer may be capable of further polymerization.- Suchcompounds can be rendered infusible and insoluble in common nonreactingsolvents.

Polymers, partial polymers and mixtures thereof with monomer can besubjected to many kinds 0! after treatment. They may be halogenated.hydrogenated, treated with sulfur dioxide, heated with sulfur, etc.

Polymers produced in accordance-with the invention contain a smallamount or hydrogen halide which tends to stabilize the polymer againstdiscoloration.

The following examples are given for the purpose oiillustratlng theinvention. Parts are on a weight basis.

Example I In each case, except for the blank, a suilicient amount orhydrogen bromide was'dissolved in a mixture of diallyl phthalate, 100parts, and bendependent upon many factors. In general, temperatu'res offrom about room temperature to about 300 C. have been used. Thepolymerization of diallyl phthalate in accordance with the invention ispreferably effected at between about 60 C. and about 250 C., employingin the lower range, e. g. 60 C. to 130 C., a catalyst such as benzoylperoxide which is effective and relatively stable in that range and inthe higher range, e. g. 130 C. to 250 C., a catalyst such as tertiarybutyl hydroperoxide or a di(tertiary alkyl) peroxide. It is sometimesdesirable to polymerize in two or more different steps, using differenttemperatures and/or different catalysts.

The. polymerization reaction can be carried to completion withoutsubstantial interruption, or it can be stopped at any point short ofcompletion. In the case of resin-forming compounds incompletepolymerization can be used for the production of a syrup comprising amixture of monomer and polymer which can be further worked andeventually substantially completely polymerized. The syrup may, forinstance, be transferred to a mold-of any desired configura tion andagain subjected to polymerization conditions or it may be used incoating operations or in the impregnation of bibulous, e. g. porous,material which, in turn, may be used in the production of laminates.Unreacted monomer may zoyl peroxide, 2 parts, to give -a solution havingthe indicated concentration or bromine, based on the weight of diallylphthalate present. -Each solution was placed in a glass vessel, whichwas then sealed and held at 65 C. for 144 hours, following which thehardness and color of the resulting resin' were determined. The blankconsistedot a mixture or diallyl phthalate, 100 parts, and benzoylperoxide, 2 parts.

Properties of Resin Percent Br Color No. Hardness None l 8 I 35 0.28 3+33 0.55.-.. 2 2s The same procedure and proportions are used in thepolymerization of methyl methacrylate.

Example II Example 111 Resins are produced in accordance with 'ExampleI, except that hydrogen iodide is' used instead of hydrogen bromide. Ineach case the products are lighter in color and slightly less hard thanthe blank, which contained no hydrogen halide.

Example IV A mixture of diallyl phthalate, parts, diallyl diglycolate,10 parts, and benzoyl peroxide, 2 parts, is admixed with sufilcien'thydrogen bromide to give a solution containing 0.5 part of bromine perparts of the combined weight of diallyl phthalate and diallyldiglycolate. The

solution is polymerized'in accordance with the procedure outlined inExample I.

I claim as my invention:

1. In a process wherein a resin is termed by the polymerization ofdiallyl phthalate in the presence 01 an organic peroxide catalyst and inthe absence of solvents and non-solvent diluents for the diallylphthalate, the improvement which comprises avoiding discoloration of theresin by eflecting said polymerization in the presence of from 0.01% to1% 01 hydrogen bromide.

2. In a process wherein a resin is formed by the polymerization ofdiallyl Dhthalate in the presence of an organic peroxide catalyst and inthe absence of solvents and non-solvent diluents for the diallylphthalate, the improvement which comprises avoiding discoloration of theresin by efleoting said polymerization in the presence of from -0.01% to1% of a hydrogen halide.

3. In a process wherein a resin is formed by the polymerization of anaromatic polycarboxylic acid ester of a beta,gamma-monooleflniomonohydric alcohol having the carboxyl carbon atoms directly attached toan aromatic ring, which polymerization is effected in the presence of aperoxide catalyst and in the absence of solvents and non-solventdiluents for said ester, the improvement which comprises avoidingdiscoloration by conducting said polymerization in the presence oi from0.01% to 5% 01' a hydrogen halide.

.4. In a process wherein a resin is formed by the polymerization of anaromatic polyoarboxylic acid ester of an unsaturated alcohol wherein theunsaturation is olefinic and the carboxyl carbon atoms are directlyattached to an aromatic ring, which polymerization is eilected in thepresence of a peroxide catalyst and in the absence of solvents andnon-solvent diluents for said ester, the improvement which comprisesavoidin the discoloration by conducting said polymerization in thepresence of from 0.01% to 5% of a hydrogen halide.

5. In a process wherein a resin is formed by the polymerization oidiallyl diglycolate in the presence of an organic peroxide catalyst andin the absence of solvents and non-solvent diluents for the diallyldiglycolate, the improvement which comprises avoiding discoloration ofthe resin by eflecting said polymerization in the presence of from 0.01%to 1% of hydrogen bromide.

6. In a process wherein a resin is formed by the polymerization of anunsaturated ester or a polycarboxylic acid, which acid is devoid of anyunsaturated linkage between any two carbon atoms of aliphatic character,and wherein the hydrogen atom of at least one of the carboxyl groups ofthe acid is replaced by an unsaturated aliphatic hydrocarbon radicalwherein the unsaturatlon is oleflnic, which polymerization is eflectedin the presence of an organic peroxide catalyst and in the absence ofsolvents and nonsolvent diluents for said ester, the improvement whichcomprises avoiding discoloration by conducting said polymerization inthe presence of from 0.01% to 5% of a hydrogen halide.

EDWARD C. SHOKAL.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name I Date 2,146,735 Hale Feb, 14, 19392,194,205 Kenyon et a1. Mar. 19, 1940 2,222,967 Wollthan et a1. Nov. 26,1940 2,231,905 Hanford et a1. Feb. 18, 1941 2,307,157 Quattlebaum et a1.Jan. 5, 1943 2,310,731 DAlelio Feb, 9, 1943 2,332,900 D'Alelio Oct. 26,1943

